Well, that is.
The range is 0-255. So when I send 255, the Arduino sends it as a binary code (11111111), because this is how the sensor perceps.
I mean, this is what the datasheet is telling me. An 8-bit code which can be translated into a decimal.
Sorry for my mistake regarding the registers.
Is there a more simplistic approach? If it would be, I'll be much glad.